This invention relates to an independent wheel suspension of motor vehicles.
In wheel suspensions of this type (compare I. Reimpell, "Fahrwerktechnik 1"; 4th Edition, Page 380) overturning moments occur as a result of the wheel contact force and the lateral distance between the supporting joint (on the wheel carrier) of the lower suspension link forming the one transverse link and the longitudinal center plane of the wheel. Such tilting moments must be absorbed by the upright shock absorber of the upper suspension link, which is elastically supported by its piston rod in the upper suspension joint fixed to the vehicle body. The shock absorber in turn is stressed by a bending moment in the transverse direction of the vehicle, and is thus deformed toward the vehicle's interior. Therefore, as a result of high breakaway forces particularly between the piston rod and the upper piston rod guide of the shock absorber cylinder, high frictional forces cause a sluggishness of the shock absorber and a substantial wear of the upper piston rod guide.
It is therefore an object of the invention, to provide a wheel suspension of the type referred to above, with significantly improved displaceability of the piston rod in the shock absorber cylinder which is impaired by overturning moments of the wheel carrier.
This object is achieved according to the invention, in which the torque generated by the prestressed upper shock absorber guiding joint seeks to rotate the shock absorber cylinder, essentially by way of the piston carried by the piston rod, in the transverse direction of the vehicle toward the exterior of the vehicle. Thus, with respect to the bending moment exerted on the shock absorber by the wheel carrier, a countermoment tends to qualify its deformation. This leads to a radial stress removal from the upper piston rod guide in the shock absorber cylinder, so that the upper suspension link, particularly in the design position of the wheel suspension, operates smoothly and has a longer service life.
In one embodiment of the invention, bracing of the upper guiding joint is advantageously achieved by a spring formed by the rubber body, which ensures a reliable wheel suspension. The rubber body may be vulcanized in between an inner and an outer bearing part, which is advantageous for desired bearing elasticities because overstraining of the rubber caused by shearing forces can be avoided.
For an upper guiding joint with more than one rubber body, in a preferred embodiment of the invention, two preferably ring-shaped rubber bodies, which can be braced with respect to one another in the axial direction of the piston rod and have a wedge shape in the lateral view, are each supported on mutually opposite sides of a piston rod flange, coaxially to the piston rod, and are assigned to one another such that the circumferential section of the rubber body which has the largest axial thickness is disposed opposite the circumferential section of the other rubber body, which has the smaller axial thickness.
In order to achieve a desirable coordination of their elasticities, the rubber bodies, particularly on their front face facing the piston rod flange, may, if necessary, also be provided with a surrounding groove-type indentation, the depth of which changes along the circumference.
In another preferred embodiment, the upper guiding joint is a ball joint, which ensures exact wheel suspension in that the rubber body, may be designed to be quite still for the support of lateral and longitudinal forces, in the radial direction, but at the same time very soft with respect to rotation. Such an arrangement permits corresponding wobbling movements of the inner bearing part, particularly in the case of a steered wheel.
When such a guiding joint is used in a wheel suspension for heavy commercial vehicles, such as buses, it is also advantageous to design the rubber body as a rubber metal element. In this manner, in addition to an overstraining of the rubber caused by shearing forces, the required high radial bearing stiffness can be ensured at the same time for the support of correspondingly high transverse and longitudinal forces.
A further embodiment of the rubber body makes it possible to minimize the installation height of the guiding joint, and to optimize its torsional softness. The ball joint may also be designed so that it minimizes the distance in the design position between the center of the ball joint and the upper piston rod guide of the shock absorber cylinder pipe. As a result, because of the given bearing prestress, a correspondingly minimal bending moment is exerted on the piston rod which, in turn, permits a reduction of the rod diameter.
The ball joint can also be designed so that the upper guide bearing is easily mounted on the shock absorber, and tensile and pressure forces as well as of torque are advantageously supported by way of the inner bearing part on the piston rod.
A final embodiment of the invention makes possible a further reduction in deformations of the shock absorber cylinder pipe resulting from bending moments.
The invention is equally advantageously suitable for wheel suspensions of steering or non-steering vehicle axles, in which case, these may be powered or not powered.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.